I needed an http proxy for another project (more on that later) and thought it would be fun to write one in ruby. How simple can it be? With a few compromises, it can be very short indeed:
I'm cheating in a couple places. I'm only handling GET requests, and I'm using Hiroshi Nakamura's excellent http-access2 package.
On the other hand, it's multi-threaded and it handles redirects, a must for the web.